January 21, 2016
Most Life That Evolved On Other Planets Died Off Long Ago

If life on a planet does not evolve fast enough it doesn't get powerful enough before natural changes in climate wipe it out. Australian researchers present the Gaian Bottleneck hypothesis:

"The mystery of why we haven't yet found signs of aliens may have less to do with the likelihood of the origin of life or intelligence and have more to do with the rarity of the rapid emergence of biological regulation of feedback cycles on planetary surfaces," he said.

Wet, rocky planets, with the ingredients and energy sources required for life seem to be ubiquitous, however, as physicist Enrico Fermi pointed out in 1950, no signs of surviving extra-terrestrial life have been found.

A plausible solution to Fermi's paradox, say the researchers, is near universal early extinction, which they have named the Gaian Bottleneck.

"One intriguing prediction of the Gaian Bottleneck model is that the vast majority of fossils in the universe will be from extinct microbial life, not from multicellular species such as dinosaurs or humanoids that take billions of years to evolve," said Associate Professor Lineweaver.

Take Mars for example. Over 3.5 billion years ago Mars had much more atmosphere and water. But the solar wind stripped away its atmosphere away. Earth's magnetic field protects our atmosphere from solar wind but Mars lacks that protective layer. Imagine that highly intelligent Martians had evolved before it lost its atmosphere. Perhaps they could have done climate engineering to build up protections for their atmosphere. But absent a sufficiently intelligent life form to intervene to protect it Mars life was doomed. Though perhaps some microorganisms still survive there underground.

Share |      Randall Parker, 2016 January 21 08:19 PM 

BernardZ said at January 24, 2016 1:31 AM:

It is not a solution but its a factor that say reduces the possible ETIs by a third - out of Venus, Mars and Earth only one produced an ETI.

akarlin said at January 27, 2016 8:09 PM:

This sounds plausible.

Korotayev and Markov found that biodiversity on planet earth seems to have followed a hyperbolic trend in terms of complexity (https://www.researchgate.net/profile/A_Korotayev/publication/222649358_Phanerozoic_marine_biodiversity_follows_a_hyperbolic_trend/links/0912f4ffd937ed6ec9000000.pdf). But the fit isn't that good - the first peak in complexity 450ma would not be superceded until 100ma. Lots of big shocks that repeatedly brought it down.

Note that the Earth is only expected to be good for life only for another 1 billion years or so. Had the hyperbolic trend on this planet been even modestly weaker, or if shocks had been substantially stronger and/or more frequent, then its quite possible that the biodiversity explosion that ushered in high level intelligence would have never occured.

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